1. Field of the Invention
The present invention relates to supporting emergency calls in, for example, an IP (Internet Protocol) based mobile network. More particularly, the present invention relates to a technique for enabling an emergency call callback of a mobile terminal, such as a mobile terminal, which does not have valid subscriber identity, such as a SIM (Subscriber Identification Module).
2. Description of the Related Art
In the United States, the FCC (Federal Communications Commission) has a requirement that an emergency call center should be able to call back a caller who has made an emergency call if the call was dropped. In the case of a caller calling from a mobile terminal, upon an emergency call being dropped, the mobile network is likely to perform paging for the terminal/subscriber who made the emergency call initially. However, if the caller made the call from a mobile terminal, which did not have a valid subscriber identity, such as a SIM, the network cannot perform paging since it does not know the identity of the caller.
In accordance with the present invention, upon a caller making a call from a terminal to a called party without a valid subscriber identity, the terminal is temporarily assigned an temporary subscriber identity. The temporary subscriber identity includes a call back identity which the called party can use to identify the caller terminal when calling the caller terminal back. The call back identity can be a CBN (Call Back Number), such as an E. 164 number, which can be later used to establish a connection to the called party.
Furthermore, in accordance with the present invention, the temporary subscriber identity includes, for example, a TMSI (Temporary Mobile Subscriber Identity) or IMSI (International Mobile Subscriber Identity), which can later be used to establish a connection to the called terminal.